more colorful baseband TV

ericballericball Posts: 772
edited 2010-10-06 - 15:54:02 in Propeller 1
As I suggested in http://forums.parallax.com/showthread.php?t=123324, the auralsub pin on the Demoboard (and others) can be used to increase the number of colors which the Propeller can display in baseband composite mode. Attached is a modified version of TV.spin which uses this idea and a demonstration program which displays a color grid using both TV.spin and my TVplus4.spin.
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Links to Propeller stuff I've done (mostly composite video)

Comments

  • Cluso99Cluso99 Posts: 14,911
    edited 2010-10-03 - 22:57:25
    Have not yet had time to check this out but it sounds great Eric :smilewinkgrin:
    My Prop boards: P8XBlade2, RamBlade, CpuBlade, TriBlade
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  • RaymanRayman Posts: 9,459
    edited 2010-10-04 - 06:06:12
    Great idea. That pin is rarely used, so why not use it for more colors...

    What resistor value should one use on the aural pin?
    Is it the standard 560 Ohms?

    Wouldn't it be better to use something like 100 Ohms for a better DAC ?
    Prop Info and Apps: http://www.rayslogic.com/
  • ericballericball Posts: 772
    edited 2010-10-04 - 06:45:44
    Rayman wrote: »
    Great idea. That pin is rarely used, so why not use it for more colors... What resistor value should one use on the aural pin? Is it the standard 560 Ohms?
    Wouldn't it be better to use something like 100 Ohms for a better DAC ?

    The standard auralsub resistor is 560ohms, and that's what's on the Demoboard. Yes, a lower resistance (400ohms) would allow Y=0 to be pushed up to blank, rather than blacker-than-black.

    A bigger improvement would be to have the 4th pin be a higher resistance (i.e. 750ohm) then use S-Video mode for burst only. (And add a 5th pin at 400ohms for sync/blank.) That would mean the saturation of the colors would be 50% more.
    Pay for your free software - let the developers know how much you appreciate their work!

    Links to Propeller stuff I've done (mostly composite video)
  • BaggersBaggers Posts: 2,965
    edited 2010-10-04 - 09:04:08
    Nice mod ericball, looks great, that's added more of a smoother colour range! :D
  • rokickirokicki Posts: 1,000
    edited 2010-10-04 - 11:13:03
    Pics or it didn't happen.
  • potatoheadpotatohead Posts: 9,714
    edited 2010-10-04 - 12:56:48
    LOL!!

    I'll do a capture or two later today. Can't wait.

    @Eric: Can you refresh me on S-video mode settings and output? I was looking for this the other day, and can't find it.
    Do not taunt Happy Fun Ball! @opengeekorg ---> Be Excellent To One Another SKYPE = acuity_doug
    Parallax colors simplified: https://forums.parallax.com/discussion/123709/commented-graphics-demo-spin<br>
  • Ahle2Ahle2 Posts: 952
    edited 2010-10-04 - 13:14:10
    I don't know if it's my TV or for some reason blacker than black levels are mixed into the visible part of the picture, but it doesn't sync. :(
    SIDcog - The sound of the Commodore 64 in a single cog: Thread, OBEX
  • jazzedjazzed Posts: 11,803
    edited 2010-10-04 - 13:28:16
    @ericball, nice idea.

    It worked for me mostly even with the 4th resistor value too high; it did lose sync periodically though (impedance mismatch artifact?). It seems very nice for a tile driver display ... maybe someday a 256 color small pixel raster driver with fast external memory would also work.

    Cheers.
  • ericballericball Posts: 772
    edited 2010-10-04 - 13:41:29
    One note: some TVs (like LCDs?) may react badly to PWM. Baggers said NTSC looked fine, but PAL wasn't good. Adding some capacitance to ground or a choke inductor might clear this up. The display was fine on my NTSC TV, but not on a portable LCD+DVD. The demo also shows the full color grid using TV.spin (first screen) and the 1 line may cause sync problems.

    @rokicki - I haven't replaced my PCI capture card after upgrading.
    @potatohead - if Chroma0 (VCFG[26]) = 0 and the VPins[7 or 3] = 1 then the color PSK is output to pin 3 or 7 rather than being mixed into pins 0-2.
    @jazzed - The Video Generator is only capable of 136 colors. My changes are exclusively to the output, not the tile descriptions. It is certainly possible to use external memory for video, the limitation is bandwidth and concurrent access.
    Pay for your free software - let the developers know how much you appreciate their work!

    Links to Propeller stuff I've done (mostly composite video)
  • jazzedjazzed Posts: 11,803
    edited 2010-10-04 - 14:36:46
    ericball wrote: »
    One note: some TVs (like LCDs?) may react badly to PWM. ... The display was fine on my NTSC TV, but not on a portable LCD+DVD. The demo also shows the full color grid using TV.spin (first screen) and the 1 line may cause sync problems.
    This sounds exactly like what I saw on my LCD+DVD. Too bad.
  • potatoheadpotatohead Posts: 9,714
    edited 2010-10-04 - 19:49:20
    @eric: Thanks!!

    I can confirm that many TV's won't tolerate the sync level in the display. The worst place for it is early or late in the scan line. Many TV's will latch onto that in a irregular way. If those levels are to be used, put them in the middle, and don't make 'em too big.

    (found that out with the potatotext color table)

    Re: Colors... Many more colors are possible, even without the changes here. Artifacting can deliver 1K colors easily, at a resolution of 160 pixels in the safe area. See the Wiki. There is a screenie with 400+ there, and I didn't use the high sat colors, which would have more or less doubled that performance.

    Ram is at issue, as always. On PAL, and to a lesser extent NTSC, there are some other schemes that can produce more than 160 colors, at a higher resolution. They use vertical banding, and can look very good, depending on what is done.

    Getting setup for some captures now... (grin)

    I'm liking this mod actually. Been struggling with project throughput time right now, and honestly, I think it makes great sense to optimize this TV.spin Lots of stuff works with it, and a few "modes", in particular a "scan buffer" mode, would make porting lots of stuff easier, and it has the PAL support, which has been sort of kicking my ***. (potatotext timings are very NTSC dependent, and I've been just stalled on a rewrite of that whole thing)
    Do not taunt Happy Fun Ball! @opengeekorg ---> Be Excellent To One Another SKYPE = acuity_doug
    Parallax colors simplified: https://forums.parallax.com/discussion/123709/commented-graphics-demo-spin<br>
  • potatoheadpotatohead Posts: 9,714
    edited 2010-10-05 - 13:18:02
    Here are the captures, for those wanting to check it out. Sorry about the PAL ones. I didn't get a chance to tweak on the PAL output prior to capture.

    The first two are PAL. New color generation code first, from the left.
    768 x 576 - 301K
    768 x 576 - 280K
    720 x 540 - 182K
    720 x 540 - 269K
    Do not taunt Happy Fun Ball! @opengeekorg ---> Be Excellent To One Another SKYPE = acuity_doug
    Parallax colors simplified: https://forums.parallax.com/discussion/123709/commented-graphics-demo-spin<br>
  • ericballericball Posts: 772
    edited 2010-10-05 - 13:24:26
    potatohead wrote: »
    Here are the captures, for those wanting to check it out. Sorry about the PAL ones. I didn't get a chance to tweak on the PAL output prior to capture.

    Thanks Doug. The ones with the + in the corner are using TVplus4.spin while the others are using TV.spin. The TV.spin picture might have sync issues due to the 1 line (note: just the colors are 1, Y=0 and Y=1 display Y=2), the TVplus4.spin picture might have sync issues (or other corruption) due to the PWM.
    Pay for your free software - let the developers know how much you appreciate their work!

    Links to Propeller stuff I've done (mostly composite video)
  • potatoheadpotatohead Posts: 9,714
    edited 2010-10-05 - 13:26:05
    My capture was cranky on these, BTW. I've not yet time to go really play with it right now, or I would. Normally, it latches on to most anything. These lost sync, on occasion, both drivers.

    Need to run on a few TV's to see where it's really at.

    Oh, and it was a $%(#$&%($% cable! Not software, not the capture device. Easy fix.
    Do not taunt Happy Fun Ball! @opengeekorg ---> Be Excellent To One Another SKYPE = acuity_doug
    Parallax colors simplified: https://forums.parallax.com/discussion/123709/commented-graphics-demo-spin<br>
  • rokickirokicki Posts: 1,000
    edited 2010-10-06 - 15:54:02
    Wow, that's really impressive!
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